Stevia Extract Production Wastewater Treatment: Ethanol Wash, Leaf Resin and Colour

Stevia sweetener is made by soaking the dried leaf in hot water or ethanol, separating the liquid from the spent leaf, and purifying the extract with resins and membranes. The water that leaves is a botanical effluent with an extraction plant attached. Spent extraction solvent carries dissolved stevioside, leaf resin and the green and brown pigments from the leaf. Spent leaf washing water carries the fine plant fraction. Purification and resin regeneration adds the wash and regeneration streams. The effluent is coloured, biodegradable and occasionally resinous enough to blind an ordinary biological stage, and the design that works recovers the solvent early, breaks the resin with coagulation, and treats the colour as a consent question.

Where the Load Comes From

Spent extraction solvent is the strongest stream. It carries dissolved stevioside, leaf resin and the pigments from the leaf, and its COD is high enough to need anaerobic treatment rather than a conventional aerobic basin.

Spent leaf washing water carries the fine plant fraction. It settles well when fresh and blinds screens when it mats.

Purification and resin regeneration adds the wash and regeneration streams, chemically active and small in volume.

Evaporator and dryer condensate is warm and dilute, and its volume is what the equalisation tank is sized against.

Solvent Recovery First

Ethanol is recovered by distillation where the volume justifies it, and the recovered solvent returns to the extraction circuit. Every litre recovered is a litre not discharged. A related discussion worth reading here is Maple Syrup Production Wastewater Treatment.

The condensate after recovery is still coloured and it still carries resin, but its solvent load is gone, and the treatment plant is then sized for what remains. Plants dealing with comparable loads face many of the same trade-offs covered in Soaking, Milling and Base Rinses.

The economics decide it. Recovery pays where the extraction runs continuously; small batch plants treat, and they size for the wash load plus the condensate rather than the average.

Dissolved resin and pigment are broken with coagulation. A polyelectrolyte sweep at controlled pH collapses the resin and the colour together, and dissolved-air flotation lifts the floc out.

Where the colour is dissolved rather than particulate, an oxidation step follows coagulation, and the design accounts for the dose from the start rather than discovering it in operation.

The recovered solids are collected rather than washed back into the drain, and the dewatering step is specified with the sticky resin floc in mind.

Biological Treatment

After coagulation and flotation, the remaining load is still strong, and anaerobic treatment is the natural first choice. Upflow anaerobic reactors take the load efficiently where volumes justify them, and the biogas offsets the facility's thermal demand.

What This Looks Like in Practice

One reference point: a 5 m³/day installation we delivered in Taishan, Guangdong (2021) was treating feed at roughly 1,000 mg/L COD and holding discharge near 50 mg/L, about 95% removal.

Figures are site-measured values from commissioned plants, not modelled estimates.

The aerobic stage behind the anaerobic one is sized modestly, and it handles the residual carbon comfortably. The nutrient balance is a design line item rather than an afterthought.

Polishing, where a sensitive receiver applies, is a sand or membrane step, and its fouling rate is a good early indicator of how well the upstream resin removal is running.

Operating Notes

Recover the solvent before you treat the water. Solvent that returns to the circuit is solvent you never have to account for. For the reuse angle specifically, Calcium Sulfate, Sulfate and High COD goes further than we can here.

Break the resin mechanically. Biology does not eat pigment, and colour that survives to the outfall is a consent question. If your site also runs this kind of duty, Chitin and Chitosan Production Wastewater Treatment covers the cost side of the decision in more depth.

Watch the sludge. Resinous floc dewaters worse than ordinary biological sludge, and it shows up on the filter cake first.

Integrated Treatment Strategies

We have written about the downstream implications separately in spodumene lithium concentrate processing wastewater treatment. Most facilities do not run a single clean stream, and a shared equalisation and biological stage is usually the economical answer once the streams are chemically compatible.

Why Choose Baihuipu as Your Manufacturer

Picking a supplier for this kind of plant is mostly about who carries the risk when something goes wrong. We have built this equipment for more than twenty years, and we are the ones who fabricated it, programmed the controls and will still answer the phone three years from now.

Own Factory, Real Capacity

Tanks, skids, control panels and membrane housings are built in our own Guangdong facility. Nothing critical is subcontracted, which is why we can commit to delivery dates and hold quality across a batch instead of hoping the shop floor gets it right.

Experience Built the Hard Way

Since the early 2000s we have commissioned plants for food and beverage processors, chemical works, electroplaters, textile mills, mines and municipalities. The lessons that stick are scaling, fouling and sludge handling — those inform every design we issue.

Documentation You Can Actually Audit

Each system ships with as-built drawings, material certificates, welding records and a functional specification. If a client's own consultant wants to review the process calculation basis, we hand it over rather than treating it as proprietary.

Complete System Responsibility

One supplier, one process guarantee. We take the plant from preliminary screening through to membrane separation, evaporation and brine management, with process, mechanical, electrical and controls engineering handled internally.

Spare Parts and After-Sales Support

We carry membranes, pumps, blowers, diffusers and instruments for every system we supply. Remote support through the PLC is standard on most builds, and on-site service covers commissioning, training and urgent callouts.

Certification and Export Practice

CE marking is standard and we work to ISO 9001 procedures. Where a project calls for specific material grades, pressure vessel certification or ATEX-rated equipment, we build to that standard and ship the full documentation pack.

Let's Look at Your Numbers

Share your water analysis and site constraints and we will give you a straight assessment of the process route and the realistic operating cost before you commit to anything. Contact our engineers at WhatsApp: +86 13631765076, or find us at hkbhp.com.

WhatsApp: +86 13631765076

Frequently Asked Questions

What spare parts should we hold on site?

Critical spares are pumps, dosing valves, instrumentation sensors and any specialty media. We ship a recommended spares kit with the plant and hold stock for everything we supply, so lead times on replacements stay short.

Do you handle installation and operator training?

Every unit we supply is commissioned by our own engineers. Training happens on site with your actual operators, and the O&M manual covers routine work plus troubleshooting. Remote diagnostics through the control system are included for the first year.

How long does a stevia extract production system take to deliver?

Standard units ship in about 9 to 11 weeks. Custom trains with solvent recovery first included run longer — plan for 17 to 20 weeks once detailed engineering starts. Site installation and wet commissioning add another few weeks.

Which discharge standard will the treated water meet?

We design against whatever consent applies at your boundary — GB 8978, local sewer limits, or a ZLD target with no liquid discharge at all. The design basis is agreed in writing before fabrication, so there is no argument later about what "compliant" meant.

Is stevia extract production treatment suitable for water reuse?

Usually yes, once the solvent recovery first stage is stable. Reuse normally means adding membrane polishing to bring conductivity and COD down to your process water specification. We would need to see your reuse water limits to size it properly.

What treatment capacity do you normally design for stevia extract production?

Skid-mounted units cover roughly 45 to 707 m³/day depending on the duty, and parallel trains extend that further. We size against your actual peak hour flow rather than the daily average, because equalisation rarely absorbs the whole spike.